Setting up DJM-850 with rekordbox DVS

Hi, New to rekordbox. Been mixing with vinyl for decades. I’m trying to connect my DJM-850 to my MacBook Pro. I’ve connected the USB to my Mac, carried out both the registration for rekordbox and rekordbox DVS. I have switched my channels to USB 1/2 and 7/8 and I have downloaded the DJM 850 driver from the drop down menu in the settings in rekordbox. When I click on midi I can see my mixer but when I get to the drop down audio in the preferences my mixer is nowhere to be seen. Can anyone help as it’s driving me up the wall. Thanks in advance Ed